Electron multiplying device



Feb. 25, 1941. R.'w. A. BREWER ELECTRON MULTIPLYING DEVICE Filed Feb.15, 1958 INVENTOR WITNESS object is to surface contours of Patented Feb.25, 1941 PATENT OFFICE 2,232,900 ELECTRON MULTIPLYING DEVICE Robert W.A. Brewer, J enkintown, Pa, assignor to Radio Corporation of America,New York, N. Y., a. corporation of Delaware Application February 15,1938, Serial No. 190,578

8 Claims. (Cl. 250-475) This invention relates to electron multipliersand more particularly to devices for causing secondary emission ofelectrons, whereby certain advantages are obtained in improving andcontrolling the electronic output and in simplifying and rigidifying thestructure of the elements, to attain this end.

The objects of my invention are: First in an electron multiplier, meansforobtaining discharges of secondary electrons by impact of primaryelectrons on ridged surfaces of unit construction and of such sturdyform .and character as can be made easily and held firmly in position inthe device.

Another object of my invention is to provide such a general form ofstructure as can be disposed in various geometrical locations. Anotherprovide interrupted emissive surf-aces which can be located at anydesired distance apart, to permit a length of electron path to suit anyrequired conditions of the actuating means.

Another object is to provide an electron emissive element of such shapeand contour of its emissive surface as to interrupt the flow of theelectron stream to cause successive impact upon the emissive element.

Another object is to provide a form of construction of secondaryemissive elements which I can be used in known general types ofelectronic tubes for example hot cathode, cold cathode, photosensitive,magnetically controlled or electrostatically controlled.

It will be seen that by a suitable combination and form of the meanshereinafter described, convenient and effective methods of producingelectron multiplication can be attained. As distinct from previouspractice of providing a number of separate frail elements to causeimpactof the electron stream, my present novel invention combines thefunctions of such elements, each in one simple, sturdy structure whichcan be made as a single unit and sealed into the enveloping tube orcasing of an electron multiplier, in a simple and reliable manner.

It is .to .be understood that I do not limit myself to this disclosureof the species of my invention,

as various embodiments of the same may come within the scope of theclaims.

To the above ends, and for the purpose of illustrating my invention, Ihave shown in the accompanying drawing forms thereof which are atpresent preferred by me, since they will give satisfactory and reliableresults. It understood that the various instrumentalities of which myinvention consists can be variously arranged and my invention is notlimited to the precise arrangement as herein shown and described.

Fig. 1 represents a side elevation, partly in section of a phototubeembodying my invention.

Fig. 1a is a side elevation of an element 4 on line la of Fig. 1. \r

Fig. 1b is a view partly in section on line lb of Fig. 1.

Fig. 1c is a plan on Fig. 2 represents an the base of Fig. 1.

elevation, partly in section, of a thermionic tube embodying myinvention.

Similar numerals of reference indicate corresponding par-ts in thefigures.

Describing the drawing in detail, the apparatus comprises an evacuatedtube or case 1. One end of the tube is sealed to a stem or press 2. Thispress carries the mounting means 3, 3 of the elements 4, 4' which formthe subject matter of my invention. In addition the press carries theelectrical connections 5, 5 in Figs. 1 and 2 and the filamentconnections 6 and B in Fig. 2, the leads are connected to the pins 1 inthe usual manner.

An anode 8 is placed in any convenient position. Refer-ring to Fig. 1,for phototubes the anode is near the base, the emitting surface of thecathode for primary electrons is located at the upper end 9 of one ofthe elements 4. The photo emissive area I0 is acted upon by a light beamll through the window [2 and the path of the electrons is thence alongthe tube to the anode B. In its travel to the anode, the beam ofelecimpressed thereon as described in known manner.

A filamentary electrode extension 13 is shown on the drawing Fig. 2 andmay be used attached to the anode 8. Alternative circuit arrangements ofknown types may be used, the two elements 4, 4 may be maintained withapo'tential gradient lengthways and constructed to have high electricalresistance. For this purpose the said elements can be made of glasscoated with mineral oxides in known manner. The potential of thefilament extension may be of any desired degree for the purpose requiredto ensure its functioning. A high frequency oscillating circuit maycouple the elements which form the subject matter of my invention or anyother known means for causing the acceleration of the electron flow.

In the construction of the elements described, the abutments causescattering of the secondary electrons and their direction of flow pathwill be influenced by the fields of. force set up as described. In Fig.2 a thermionic emitter is indicated, the radially heated cathode M isshown coacting with the filament H: which is supported by leads 6carrying the heating current and at tached to the usual pins 16, It,when alternating current is used. The emit-ting cathode has an apertureI! which can be disposed to discharge electrons against the element 4'at its extremity.

trons is bombarded against the interrupting surfaces of the elements 4,4, back and forth from one to-the other, and is urged in these movementsby electroestatic or electro-magnetic forces to another,

Direct current can be employed in known manner and .the element Momitted, this, or any other means of originating the primary electronstream does not form part of my invention.

This type of electron multiplier is preferred for use in industrialapplications for direct connection to a relay or other similar device,without intermediate amplification.

It is understood that the elements 4, 4 which are the essence of thisdevice, are capable of construction in any practical manner and of anysuitable material. When glass is used as the foundation, the conductinglead-in can be sealed into the glass and a contact plate provided orother means for connecting an emissive coating to be depositedsubsequently thereon. The glass element can then be sealed into thepress making a robust connection, and it may be supported at the otherend if desired. A thin coating of oxide may be used on the glass where ahigh potential gradient is required or the elements 4, 4' may beconstructed of metal when a high frequency oscillation is used as anaccelerator.

It is not essential to my invention that the secondary emissive elementsbe electrically conductive throughout their length in every application.In certain types, when acceleration of the electrons towards the anodetakes place through definite potential steps from one area the variousinterruptions in the surelements may be electrically discontinuous. Thiseffect can be obtained by leaving breaks in the emissive surfaces when,or after the coatings are applied. When metal is used with, or withoutactivation, these metal units can be molded to the glass foundation andeach unit connected to a lead-in wire sealed into the supporting member3 or 3' and attached to suitable base pins thus formed into aself-contained sturdy unit structure.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. An electron multiplier tube comprising an envelope housing an anodeand a cathode, secondary emissive electrodes mounted between said anodeand said cathode, said secondary emissive electrodes being each composedof a series of hollow cylindrical members having their linear edgescontiguous to each other and their hollow surfaces coated with secondaryemissive material, the hollow surfaces of one series facing the hollowsurfaces of the other series.

2. An electronic multiplying device comprising an envelope, 2. pair ofsecondary emissive electrodes each having a surface formed in a singleunit, an interrupting contour on said surface formed by a series ofsubstantially semi-cylindrical elements having their linear edgesdisposed longitudinally of said envelope, an anode and a cathodedisposed within said envelope, one substantially at each end of saidsecondary emissive elements and disposed to generate an electron streambetween the interrupting contours of said secondary emissive electrodes.

3. An electron multiplying device comprising an envelope housing ananode, a cathode comprising, a source of primary electrons, a pair ofsingle unit non-conducting elements each comprising a series ofsubstantially semi-cylindrical surfaces disposed along a path betweenthe anode and the cathode and having the concave surfaces of one elementfacing the concave surfaces of the other element, said concave surfaceseach faces of my pin external of the envelope,

envelope, said emissive elements being each of 3 unit constructioncomposed of a series of substantially semi-cylindrical members havingtheir linear edges contiguous to each other and similar surfaces facingeach other and longitudinally in staggered relation to each other, saidsurfaces coated with a secondary emissive material.

5. An electron multiplier device comprising a containing envelope, ananode, a cathode comprising a source of primary electrons, secondaryemissive elements between the anode and the cathode and extendinglongitudinal of said envelope, said elements being each of unitconstruction of non-conductive material provided with a series ofsubstantially semi-cylindrical surfaces, the concave portions thereofbeing provided with conductive area coated with seconary emissivematerial, each conductive area conductively connected through thecontaining non-conductive element to an attachment pin external of thecontaining envelope.

6. An electron multiplier tube comprising an envelope housing an anodeand a cathode, sec ondary emissive electrodes mounted between said anodeand said cathode, said secondary emissive electrodes each composed of aunit structure formed as a series of substantially semi-cylindricalelements mounted in series relation between the anode and the cathodeand having their linear edges contiguous to each other and the hollowsurfaces of one element staggered with respect to the hollow surfaces inthe other element and said surfaces coated with secondary emissivematerial.

7. A secondary emissive element for an electron multiplying devicecomprising a corrugated tubular ribbon of non-conductive material and ofsubstantially rectangular external form, electron emissive conductivesurfaces disposed in the hollow faces of said element at one sidethereof, each said emissive conductive surface conductively andseverally attached to a conductor internal of said ribbon at one end ofsaid conductor and the other end of said conductor adapted to coact witha contact pin, said element to form a complete unit, two of whichcomprise an electron multiplying device when sealed into a suitablehousing containing an anode and a cathode disposed one at each end ofthe said pair of secondary emissive elements.

8. A secondary emissive element for an electron multiplier comprising ahollow stem of vitreous material, one side of said stem being fiat andformed in a series of concave surfaces, said surfaces each separatelycoated with secondary emissive material and electrically discontinuousfrom adjacent coated surfaces, each said surface electrically connectedto an insulated conductor contained in the said hollow stem andextending therethrough, contact means external of the said stem.

ROBERT Vi. A. BREWER.

said conductor connected to a

